Thus spake Tony Li
I don't see how we'd get incremental deployability with truly split address spaces.One way would be to split them in such a way that they jointly remained syntactically similar to the original address space. Thisis one of the cuter things about GSE. Then new generation systems could recognize them as split (via a compatibility bit someplace) and to legacy systems, it would appear to be a legacy address.
I suppose that's a "split"; I thought Russ was worried that there would be two (potentially overlapping) address spaces, one for providers and one for customers, as opposed to a single address space which was divided into RLOCs and EIDs. For instance, there's been mention of using IPv6 for EIDs and IPv4 for RLOCs, which has some interesting properties.
Along your lines of a split, I like the idea of using 4000::/3 for LISP-mapped EIDs and deprecating PI space in 2000::/3. It's a bit tougher to apply the same split to v4 since there won't be any /8s left by the time a solution is standardized...
If we are able to constrain BGP tables to only transit ASes, the DFZ becomes a lot smaller and we can afford to let everyone,even home users, multihome with PI space. (Of course, there's a hidden assumption there that the number of transit ASes will remain under control, but I haven't seen anyone dispute that.)There's also a hidden assumption there that you can do that. One practical definition of PI space today is that your prefix is in BGP.
That's one way of looking at it, but that's only a result of the fact that PI space _can't_ be reached today unless a prefix is in BGP. Technically, if I got a block from my RIR for internal use, it's still PI space even if it never shows up in BGP.
With LISP, I envision a world where PI space and EID blocks are the same thing, and neither shows up in the DFZ -- other than a single EID aggregate that leads to anycast ITRs (to handle legacy senders).
S Stephen Sprunk "God does not play dice." --Albert Einstein CCIE #3723 "God is an inveterate gambler, and He throws theK5SSS dice at every possible opportunity." --Stephen Hawking
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